SYDNEY (AFP) - Effective
germ-laden weapons have been developed and have the potential to cause
far greater devastation than nuclear arms, an international bio-terrorism
symposium was told Sunday.

Ken Alibek, a former Soviet bio-weapons scientist who
defected to the West seven years ago, told the symposium at the world congresses
on virology and bacteriology that the Soviet Union had successfully developed
warheads filled with anthrax, smallpox, plague and the Ebola virus.

The experiments went on into the early 1990s despite
the Soviet Union signing the international treaty banning toxin weapons
in 1972, along with 140 other nations.

Alibek said that unlike the United States, whose biological
weapons program ended in 1969, the Soviets had no compunction about developing
weapons using bacteria or viruses for which there was no treatment or preventive
vaccines.

In fact, the weapons considered to have the most potential
were those using biological agents for which there was no treatment --
such as Ebola, the related Marburg virus, and smallpox.

In addition, they developed weapons based on germs which
had been genetically engineered to be resistant to antibiotics and vaccines,
he said.

"I'm 100 percent sure that some biological weapons
have greater killing capability than nuclear weapons," he told the
symposium.

Alibek, who is now chief scientist at a US company researching
biological weapons protection, said he had worked out how much biological
material was required to devastate a population.

He estimated three kilograms (6.6 pounds) of anthrax
sprayed over one square kilometre would be enough to kill 50 percent of
people in its path.

For Marburg, the formula was just one kilogram per square
kilometre.

Former US presidential adviser Donald Henderson said
the biological weapons threats in order of concern were smallpox, anthrax,
plague, botulin toxin, haemorrhagic fever viruses and tularaemia.

Chris Davis, a former British defence intelligence and
disarmament adviser, pointed out thousands of scientists dispersed with
the break-up of the Soviet Union, taking their skills and possibly biological
material with them.

The Soviet enterprise employed more than 60,000 people
in 200 laboratories, producing multi-tonne volumes of deadly germs, he
said.

In 1995, the Japanese cult Aum Shinrikyo created chaos
on the Tokyo subway when it released the nerve gas sarin, killing 12 and
injuring at least 3,000 people.

Western governments are devoting billions of dollars
to bio-terrorism preparedness, the symposium heard.